JP3800301B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to a technical field of an image forming apparatus such as an electrostatic copying machine or a printer having a developing device that performs multicolor development of two or more colors such as full color by a plurality of developing devices mounted on a rotating body. In particular, the present invention belongs to the technical field of an image forming apparatus of a contact development type in which development is performed in a state where the developing roller of the developing device is in contact with the photosensitive member.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrostatic copying machine or a printer, there are various image forming apparatuses provided with a developing device that performs multicolor development of two or more colors such as full color by a plurality of developing devices mounted on a rotating body. Has been developed. In this image forming apparatus, a rotating body is rotated at the time of image formation, and the developing roller of each developing device is sequentially set to a developing position, and a latent image on the photosensitive body is sequentially developed for each color to form an image. Yes.
[0003]
In this type of conventional image forming apparatus, there is a contact developing type image forming apparatus in which development is performed by keeping the developing roller away from the photosensitive member during normal development and bringing the developing roller into contact with the photosensitive member during development. In this contact developing type image forming apparatus, since the developing roller comes in contact with and separates from the photosensitive member, there is a risk that the photosensitive member may be damaged by the contact and separation of the developing roller. It is suppressed when it is brought into contact with and separated from the photoconductor in the rotating state. Therefore, in order to prevent damage to the photoreceptor, it is necessary to bring the developing roller into contact with and away from the photoreceptor while the developer roller is always rotated.
[0004]
As described above, as a method of transmitting the driving force of the driving motor of the developing device to the developing roller in order to make the developing roller rotate when the developing roller contacts the photoconductor,
(a) a fixed driving gear to which a driving force of a driving motor is transmitted and a developing roller driving gear on the developing roller side, which is movably provided, is meshed during development;
(b) A drive gear that is provided so as to be able to swing and transmits a driving force of a drive motor and a developing roller drive gear on the developing roller side are engaged by swinging the drive gear that can swing during development. How to match,
(c) a method in which a driving gear to which a driving force of a driving motor is transmitted and a developing roller driving gear on the developing roller side are meshed by a rotating force of a rotary member such as a rotary during development;
Has been adopted.
[0005]
On the other hand, such an image forming apparatus needs to be initialized first after being shipped from the factory. In performing this initialization, since the developing roller is driven at a predetermined developing position, in the contact developing type image forming apparatus, as described above, in order to prevent damage to the photosensitive member, a dummy toner is previously set at the time of shipment from the factory. Is applied to the developing roller, and the photosensitive member is prevented from being damaged by the lubricating action of the dummy toner.
[0006]
[Problems to be solved by the invention]
However, in the above-described method (a) in which the driving force of the developing device driving motor is transmitted to the developing roller, the power can be transmitted only within the range of operation in which the gear and the gear are in contact with or away from each other, and therefore there is a nip. In some cases, the developing roller may come into contact with the photoreceptor before it rotates sufficiently. Also in the method (b), power can be transmitted only within the range of operation in which the gear and the gear are in contact with or separated from each other as in the method (a). There is a risk of contact with the body. Furthermore, in the method (c), when the rotation of the rotary and the rotation of the developing roller are switched, the rotation of the developing roller may stop or may not exceed a predetermined number of rotations.
[0007]
As described above, in any of the conventional methods (a) to (c) described above, there are cases where the developing roller does not rotate or does not sufficiently rotate when contacting or separating from the photoreceptor. It is difficult to sufficiently and reliably prevent damage to the photosensitive member when the developing roller is in contact with and separated from the photosensitive member.
[0008]
In addition, in the conventional image forming apparatus described above, in order to prevent damage to the photoreceptor during initialization, the dummy toner is applied to the developing roller in advance at the time of shipment from the factory. This requires not only complicated operations at the time of shipment, but also requires dummy toner in addition to developing toner, resulting in high costs.
[0009]
The present invention has been made in view of such circumstances, and an object of the present invention is to bring the developing roller into and out of contact with the photosensitive member in a state where the developing roller is reliably rotated, and to rotate the developing roller by a predetermined amount. An object of the present invention is to provide an image forming apparatus in which a developing roller can be brought into contact with and separated from a photosensitive member in a state where the number is set to several or more.
Another object of the present invention is to provide an image forming apparatus capable of simplifying the work for initialization.
[0010]
[Means for Solving the Problems]
In order to solve this problem, the invention of claim 1 includes n developing devices each having a developing roller mounted on a rotating member and capable of contacting and separating from the photosensitive member. At the time of development, the driving force of the developing device driving motor is transmitted to the developing roller sequentially through the developing device driving force transmitting means provided for each developing device, and the rotation of the rotating member causes the rotation of the rotating member. In the image forming apparatus that performs multi-color development by moving the developing roller to a developing position that sequentially contacts the photosensitive member and setting the developing roller to the developing position by stopping the rotation of the rotating member, the developing device driving force transmitting unit includes: a differential gear mechanism comprising n-1 differential gears, wherein the differential gear is provided at least with an input shaft provided rotatably, and provided with only a relative rotation on the input shaft; Have Two output gears are provided so as to revolve around the input shaft by rotation of the input shaft and to rotate about an axis orthogonal to the input shaft, and each of the bevel gears of the two output gears Each of the two output gears includes a bevel gear other than the bevel gears of each of the two output gears, and the differential gear mechanism includes a first difference of one of the n-1 differential gears. The driving force of the developing device drive motor is transmitted to the input shaft of the dynamic gear, and the output of one of the first and second output gears that are the two output gears in the first differential gear is Of the n-1 differential gears, the third and fourth output gears are transmitted to the input shaft of the other second differential gear and are the two output gears in the second differential gear. Each output and first and Any one output of the other outputs of the second output gear is transmitted to the input shaft of the other third differential gear among the n-1 differential gears. The n−1 differential gears are connected to each other, and among the output gears of the n−1 differential gears, the output gears that do not transmit output to the input shafts of the other differential gears. It is configured to take out outputs, and n outputs are obtained by the n-1 differential gears with respect to the driving force of the developing device driving motor, and these n outputs are respectively supplied to the n developing rollers. And n is n ≧ 3, and the control for controlling the differential gear mechanism so as to selectively extract an arbitrary number of outputs among the n outputs. And the control means contacts the photoconductor by rotation of the rotating body. The differential gear mechanism is controlled so that the output is taken out before the developing roller to be brought into contact with the photosensitive member reaches the developing position, and the developing roller moves from the developing position to move the photosensitive member. The differential gear mechanism is controlled so as to stop taking out the output after being separated from the position.
[0011]
According to a second aspect of the present invention, there are provided two developing devices each having a developing roller mounted on a rotating member and capable of coming into contact with and separating from the photosensitive member, and separating the developing roller from the photosensitive member when not developing. In developing, the driving force of the developing device driving motor is sequentially transmitted to the developing roller via the developing device driving force transmitting means provided for each developing device, and the developing roller is sequentially rotated by the rotation of the rotating body. In an image forming apparatus that performs multi-color development by moving to a developing position that contacts the body and setting the developing position by stopping the rotation of the rotating body, the developing device driving force transmitting means includes one differential gear. A differential gear mechanism comprising: at least an input shaft rotatably provided; and two output gears each provided with a bevel gear provided only relative to the input shaft; Said The rotation of the force shaft is provided so that it can revolve around the input shaft and can rotate about an axis orthogonal to the input shaft, and is always meshed with each of the bevel gears of the two output gears. The two output gears are bevel gears other than the bevel gears, and the differential gear mechanism transmits the driving force of the developing device drive motor to the input shaft of the differential gear. Each of the two output gears in the dynamic gear is configured to take out an output, and two outputs are obtained by the one differential gear with respect to the driving force of the developing device drive motor. Are respectively transmitted to the two developing rollers, and a control means for controlling the differential gear mechanism so as to selectively extract at least one of the two outputs. The differential gear mechanism so that the control means takes out the output before the developing roller that is in contact with the photosensitive member by rotation of the rotating member is in the developing position in contact with the photosensitive member. And the differential gear mechanism is controlled to stop taking out the output after the developing roller is moved from the developing position and separated from the photosensitive member.
[0012]
Further, the invention according to claim 3 is that when the developing roller rotated by the output of the differential gear mechanism selectively taken out by the control means reaches or exceeds a predetermined number of rotations, The developing roller is set at the developing position and is brought into contact with the photosensitive member.
Furthermore, the invention according to claim 4 is that the developing roller rotated by the output of the differential gear mechanism selectively taken out by the control means exceeds a predetermined rotational speed and a predetermined time has elapsed. Thereafter, the developing roller is set at the developing position and is brought into contact with the photosensitive member.
Further, the invention according to claim 5 is that when the developing roller rotated by the output of the differential gear mechanism selectively taken out by the control means has a predetermined number of rotations or more, the development is performed. A roller is moved from the developing position to be separated from the photoconductor.
Further, the invention according to claim 6 is directed to the differential gear mechanism selectively taken out by the control means in a state where the rotating body is set at a position where none of the developing rollers is in contact with the photoconductor. Initialization is performed by rotating each developing roller with an output.
[0013]
[Action]
In the image forming apparatus according to the first and second aspects of the present invention configured as described above, the control unit causes the differential gear before the developing roller to contact the photosensitive member reaches the developing position that contacts the photosensitive member. Since the output of the mechanism is selectively taken out, the driving force of the developing device driving motor is reliably transmitted to the developing roller that is to contact the photosensitive member via the differential gear mechanism before the developing position that contacts the photosensitive member is reached. Will be transmitted to. As a result, the developing roller always abuts on the photoconductor in a surely rotated state. Therefore, when contacting the photoconductor, a toner layer is formed on the developing roller, and the developing roller contacts the photoconductor through the toner layer. Come into contact. Further, after the developing roller in contact with the photosensitive member moves from the developing position and is separated from the photosensitive member, the output of the differential gear mechanism is stopped. As a result, the developing roller is always separated from the photoconductor while being reliably rotated, so that the developing roller is separated from the photoconductor through the toner layer. Therefore, the developing roller always rotates reliably and comes into contact with and separates from the photoreceptor in a state where the toner layer is formed. However, since the toner in the toner layer functions as a lubricant at that time, the photoreceptor is damaged. Is prevented.
[0014]
In the invention of claim 3, the developing roller always comes into contact with the photosensitive member in a state of rotating at a predetermined rotational speed or more. As a result, the developing roller comes into contact with the photoconductor in a state where the toner is more reliably supplied, and thus the photoconductor is more reliably prevented from being damaged when the developing roller comes into contact.
Further, in the fourth aspect of the invention, the developing roller comes into contact with the photosensitive member after a predetermined time elapses while the developing roller is reliably rotated at a predetermined rotational speed or more. As a result, the toner is uniformly dispersed on the developing roller, the toner layer is uniformly formed on the developing roller, and the rotation fluctuation of the developing roller is reduced, so that the photoreceptor is more reliably prevented from being damaged.
[0015]
Further, in the invention of claim 5, the developing roller is always separated from the photoconductor while being rotated at a predetermined rotational speed or more. As a result, the developing roller is separated from the photoconductor in a state where the toner is more reliably supplied, so that the photoconductor is more reliably prevented from being damaged when the developing roller is separated.
Furthermore, in the invention of claim 6, the driving force of the developing device driving motor is reliably transmitted to each developing roller in a state where none of the n developing rollers are in contact with the photoreceptor, so that the developing roller rotates. become. Therefore, the image forming apparatus can be easily initialized after shipment from the factory without damaging the photoreceptor.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 2 is a diagram showing a portion of the power transmission mechanism other than the developing roller, the supply roller, and the differential gear mechanism as viewed from the left side in FIG. 1. In FIG. 1, some of the components shown in FIG. 2 are omitted, and in FIG. 2, some of the components shown in FIG. 1 are omitted.
[0017]
As shown in FIG. 1, the image forming apparatus 1 of this example includes a rotary developing device 2, and the rotary developing device 2 is rotatably supported by a rotary 3 and supported by the rotary 3. , Yellow (Y), magenta (M), cyan (C), and black (K) developing devices 4, 5, 6, and 7. Each of these developing devices 4, 5, 6, and 7 is disposed in the circumferential direction of the rotary 3 in this order in the clockwise direction and at equal intervals. The developing rollers 4a, 5a, 6a, and 7a and the supply roller 4b are respectively provided. , 5b, 6b, 7b. As the rotary 3 rotates, each of the developing units 4, 5, 6, and 7 has their developing rollers 4a, 5a, 6a, and 7a sequentially contacted with the photosensitive member (hereinafter also referred to as OPC) 8. It has come to be. The arrangement order of the developing devices 4, 5, 6, and 7 for each color is arbitrarily set without being limited to the above-described order. However, in the following description, for convenience of explanation, it is assumed that the developing devices 4, 5, 6, and 7 are arranged in the order of the above-described colors, that is, yellow, magenta, cyan, and black.
[0018]
As shown in FIGS. 1 and 2, the image forming apparatus 1 further transmits a stepping motor 9 that is a rotary drive motor for rotationally driving the rotary 3 and the driving force of the stepping motor 9 to the rotary 3. A rotary driving force transmission means 10 for developing, a developing device driving motor 11 for rotationally driving the developing rollers 4a, 5a, 6a, 7a of the developing devices 4, 5, 6, 7 and the developing devices 4, 5, Each developing device driving force transmitting means 12Y is provided for every 6 and 7, and transmits the driving force of the developing device driving motor 11 to the developing rollers 4a, 5a, 6a and 7a and the supply rollers 4b, 5b, 6b and 7b. , 12M, 12C, 12K.
The stepping motor 9 can be stopped while the supply current to the motor is supplied by setting the hold current by the current control, so that the position can be easily set.
[0019]
The rotary drive force transmission means 10 is concentric with the rotary drive gear 10a, which is attached to the rotary shaft of the stepping motor 9 so as to be integrally rotatable, a rotary drive intermediate gear 10b that is always meshed with the rotary drive gear 10a, and the rotary 3. The rotary gear 10c is provided integrally with the rotary 3 and always meshes with the rotary drive intermediate gear 10b. The drive force of the stepping motor 9 is reduced and transmitted to the rotary 3. The rotary shaft 3a of the rotary 3 and the rotary gear 10c is rotatably supported by the frame 13 of the image forming apparatus 1.
In this case, since the first differential gear 15 of the differential gear mechanism 14 is concentrically interposed between the rotary shaft 3a and the rotary 3 and the rotary gear 10c as will be described later, the rotary shaft 3a is not connected to the rotary shaft 3a. 3 and the rotary gear 10c are spaced apart from each other in the axial direction of the central axis. The rotary shaft 3a is connected to the rotary 3 and the rotary gear 10c by an appropriate method. As an example of this connection method, as shown in FIG. 3, the disk-shaped radial connecting portion 3b whose center is fixed to the rotating shaft 3a and the end portion extending in the axial direction from the outer peripheral edge of the radial connecting portion 3b. A connecting method using a cup-shaped connecting member 3d having a U-shaped cross section composed of a cylindrical axial connecting portion 3c fixed to the rotary gear 10c is conceivable. As shown in FIGS. 3 and 4, the axial connecting portion 3c is cut away at the portion where the second and third differential gears 16 and 17 of the differential gear mechanism 14 interfere to form the differential gear relief portions 3e and 3f. Is provided. The connecting member 3d may be formed in a cup shape with a U-shaped cross section, or a predetermined number of linear members having a U-shaped cross section, an L-shaped cross section, or a J-shaped cross section may be used instead of the cup shape. In addition, any connecting member 3d may be used as long as it can connect the rotary shaft 3a to the rotary 3 and the rotary gear 10c while avoiding interference with the differential gear.
[0020]
Further, the developing device driving force transmission means 12Y, 12M, 12C, and 12K use the differential gear mechanism 14 to transfer the driving force of the developing device drive motor 11 to the developing rollers 4a, 5a, 6a, 7a and the supply rollers 4b, 5b, 6b and 7b are transmitted selectively or simultaneously. In describing these developing device driving force transmission means 12Y, 12M, 12C, and 12K, first, the principle of operation of the differential gear of the differential gear mechanism 14 employed therein will be described.
[0021]
As shown in FIGS. 5A to 5C, the differential gear α includes an input shaft β to which an input is applied, and a first and a second shaft that are supported by the input shaft β so as to be rotatable and non-movable in the axial direction. A second output gear γ, δ, a power transmission shaft ε fixed so as to be orthogonal to the input shaft β, and an intermediate bulkhead supported by the power transmission shaft ε so as to be rotatable and immovable in the axial direction of the shaft ε. It comprises a gear ζ and first and second locks η, θ that lock the first and second output gears γ, δ and stop their rotation, respectively. The first and second output gears γ and δ are spur gears γ, respectively. ₁ , δ ₁ And these spur gears γ ₁ , δ ₁ Bevel gear γ fixed to be integrally rotatable ₂ , δ ₂ It is made up of. And these bevel gears γ ₂ , δ ₂ The intermediate bevel gear ζ is always meshed with each other.
[0022]
In the differential gear α thus configured, first, as shown in FIG. 5A, when both the first and second output gears γ and δ are not locked and can be freely rotated, the input shaft β When the input is applied to the input shaft β and the input shaft β rotates, the power transmission shaft ε rotates about the input shaft β. Then, the intermediate bevel gear ζ rotates (revolves) around the input shaft β, and the first and second output gears γ and δ simultaneously rotate around the input shaft β and output by the driving force of the revolution. Become. Therefore, in this case, as shown by the arrow, in the differential gear α, the input is transmitted via the input shaft β, the power transmission shaft ε, and the intermediate bevel gear ζ, and both the first and second output gears γ and δ are transmitted. It comes to output.
[0023]
Next, as shown in FIG. 5B, when the rotation of the second output gear δ is locked by the second lock θ, when the input shaft β rotates, the driving force for the revolution of the intermediate bevel gear ζ is the same as described above. Thus, both the first and second output gears γ and δ are to be rotated. However, at this time, the intermediate bevel gear ζ is changed to the double bevel gear γ. ₂ , δ ₂ And the rotation of the second output gear δ is locked, so that the intermediate bevel gear ζ is the bevel gear δ of the second output gear δ. ₂ , While rotating (rotating) about the power transmission shaft ε. That is, the intermediate bevel gear ζ rotates around the power transmission shaft ε while revolving around the input shaft β. By the combined rotation of the revolution and rotation of the intermediate bevel gear ζ, only the first output gear γ rotates around the input shaft β and outputs. Therefore, in this case, as shown by the arrow, in the differential gear α, the input is transmitted via the input shaft β, the power transmission shaft ε, and the intermediate bevel gear ζ, and is output from the first output gear γ.
[0024]
Further, when the rotation of the first output gear γ is locked by the first lock η as shown in FIG. 5C, when the input shaft β rotates, the same as the locked state of the rotation of the second output gear δ described above. Thus, only the second output gear δ rotates around the input shaft β and outputs by the combined rotation of the revolution and rotation of the intermediate bevel gear ζ. Therefore, in this case, as shown by the arrow, in the differential gear α, the input is transmitted via the input shaft β, the power transmission shaft ε, and the intermediate bevel gear ζ and output from the second output gear δ.
Further, although not shown, when the rotations of the first and second output gears γ and δ are both locked by the first and second locks η and θ, the revolution of the intermediate bevel gear ζ is impossible, so the input shaft β is also It becomes impossible to rotate.
[0025]
In this way, the differential gear α is output from an output gear that is not locked, and by controlling the number of output gears to be locked, one output or two outputs are selectively generated for one input. It is supposed to be. In addition, when the first and second output gears γ and δ are both locked by the first and second locks η and θ, the differential gear α becomes non-rotatable when the input shaft β is non-rotatable. When at least one of the second output gears γ, δ is rotatable without being locked, the input shaft β is rotatable.
[0026]
In the differential gear mechanism 14 of the image forming apparatus 1 of this example, by combining three differential gears α, four outputs are selectively generated in an arbitrary number of 1 to 4 with respect to one input. Has been. That is, the four developing devices 4, 5, 6, and 7 are selectively driven by an arbitrary number of 1 to 4 by the driving force of one developing device driving motor 11.
[0027]
The differential gear mechanism 14 will be specifically described. As shown in FIG. 6, the differential gear mechanism 14 applies driving force to the first differential gear 15 to which the driving force of the developing device driving motor 11 is input, and to the yellow developing device 4 and the magenta developing device 5, respectively. It consists of a second differential gear 16 for transmitting and a third differential gear 17 for transmitting driving force to the cyan developing device 6 and the black developing device 7 respectively.
[0028]
The first differential gear 15 receives a driving force of the developing device drive motor 11, and penetrates the rotary shaft 3a of the rotary 3 so as to be relatively rotatable, and is supported by the rotary shaft 3a. The first and second output gears 15b and 15c are supported on the first input shaft 15a so as to be rotatable and immovable in the axial direction, respectively, and a first power transmission shaft fixed so as to be orthogonal to the first input shaft 15a. 15d and a first intermediate bevel gear 15e supported by the first power transmission shaft 15d so as to be rotatable and immovable in the axial direction of the first power transmission shaft 15d. The first and second output gears 15b and 15c are respectively the first and second spur gears 15b. ₁ , 15c ₁ And these first and second spur gears 15b. ₁ , 15c ₁ The first and second bevel gears 15b fixed to be integrally rotatable with each other ₂ , 15c ₂ It is made up of. These first and second bevel gears 15b ₂ , 15c ₂ The first intermediate bevel gear 15e is always meshed. The first differential gear 15 is not provided with a lock.
[0029]
The second differential gear 16 is rotatable to the second input shaft 16a to which the driving force of the developing device drive motor 11 is input as an output of the first differential gear 15, and to the second input shaft 16a. Third and fourth output gears 16b and 16c supported so as not to move in the axial direction, a second power transmission shaft 16d fixed so as to be orthogonal to the second input shaft 16a, and rotated to the second power transmission shaft 16d First and second intermediate bevel gears 16e supported so as to be immovable in the axial direction of the second power transmission shaft 16d and the third and fourth output gears 16b and 16c are respectively locked to stop their rotation. The second locks 16f and 16g, and a first intermediate power transmission gear 16h that is fixed to the second input shaft 16a so as to be integrally rotatable and to which the output of the first output gear 15b of the first differential gear 15 is input. ing. The third and fourth output gears 16b and 16c are respectively the third and fourth spur gears 16b. ₁ , 16c ₁ And these third and fourth spur gears 16b ₁ , 16c ₁ The third and fourth bevel gears 16b are fixed to be integrally rotatable. ₂ , 16c ₂ It consists of. The first intermediate power transmission gear 16h is a first spur gear 15b of the first output gear 15b. ₁ And the second intermediate bevel gear 16e is connected to the third and fourth bevel gears 16b. ₂ , 16c ₂ Always meshed.
[0030]
Further, the third differential gear 17 is rotatable to the third input shaft 17a to which the driving force of the developing device drive motor 11 is input as an output of the first differential gear 15, and to the third input shaft 17a. The fifth and sixth output gears 17b and 17c supported so as not to move in the axial direction, the third power transmission shaft 17d fixed so as to be orthogonal to the third input shaft 17a, and the third power transmission shaft 17d are rotated. The third intermediate bevel gear 17e supported so as to be immovable in the axial direction of the third power transmission shaft 17d, and the fifth and sixth output gears 17b and 17c are respectively locked to stop their rotation. The fourth locks 17f and 17g, and a second intermediate power transmission gear 17h that is fixed to the third input shaft 17a so as to be integrally rotatable and to which the output of the second output gear 15c of the first differential gear 15 is input. ing. The fifth and sixth output gears 17b and 17c are respectively the fifth and sixth spur gears 17b. ₁ 17c ₁ And these fifth and sixth spur gears 17b. ₁ 17c ₁ Fifth and sixth bevel gears 17b fixed to be integrally rotatable with each other ₂ 17c ₂ It consists of. The second intermediate power transmission gear 17h is a second spur gear 15c of the first output gear 15c. ₁ And the third intermediate bevel gear 17e is connected to the fifth and sixth bevel gears 17b. ₂ 17c ₂ Always meshed.
[0031]
Any one of the first to fourth locks 16f, 16g, 17f, and 17g is selectively controlled by a central processing unit (CPU) (not shown) of the image forming apparatus 1. . These first to fourth locks 16f, 16g, 17f, and 17g can be a known brake device as long as they can stop the rotation of the third to sixth output gears 16b, 16c, 17b, and 17c, respectively. Any type of lock can be used, but the structure of the lock itself is not particularly characterized in the present invention, and a detailed description thereof will be omitted.
[0032]
Next, the operation of the differential gear mechanism 14 thus configured will be described.
First, since the operation of the second and third differential gears 16 and 17 having a lock is the same as that of the differential gear α shown in FIG. 5 described above, the first differential gear 15 not having a lock is operated. The operation will be described. As is apparent from the above description of the operation of the differential gear α, both the first and second locks 16f and 16g of the second differential gear 16 are operated and both the third and fourth output gears 16b and 16c are not rotatable. The second input shaft 16a is not rotatable, and when at least one of the other third and fourth output gears 16b, 16c is rotatable, the second input shaft 16a is not rotated. Is possible. Therefore, when both the third and fourth output gears 16b and 16c are not rotatable, the first output gear 15b that is always meshed with the first intermediate power transmission gear 16h fixed to the second input shaft 16a is not rotatable. When at least one of the other third and fourth output gears 16b, 16c is rotatable, the first output gear 15b is rotatable. Similarly, when both the fifth and sixth output gears 17b and 17c of the third differential gear 17 are not rotatable, the second intermediate power transmission gear 17h fixed to the third input shaft 17a is connected to the second intermediate power transmission gear 17h. The second output gear 15c that is always meshed is not rotatable, and when at least one of the other fifth and sixth output gears 17b, 17c is rotatable, the second output gear 15c is rotatable. is there.
[0033]
That is, the first output gear 15b of the first differential gear 15 is locked when both the first and second locks 16f and 16g are operated, and when at least one of the first and second locks 16f and 16g is not operated. Not locked. Similarly, the second output gear 15c of the first differential gear 15 is locked when both the third and fourth locks 17f and 17g are operated, and at least one of the third and fourth locks 17f and 17g is operated. It is not locked when not done.
[0034]
As is clear from this, the differential gear mechanism 14 is output from the output gears that are not locked among the third to sixth output gears 16b, 16c, 17b, and 17c, similarly to the differential gear α described above. become. Therefore, the differential gear mechanism 14 selectively generates one to four outputs for one input by controlling the number of output gears to be locked.
[0035]
As shown in FIGS. 1 and 2, each developing device driving force transmitting means 12Y, 12M, 12C, 12K has a first input shaft 15a rotatably supported on the frame 13 concentrically with the rotary 3, and second and A differential gear mechanism 14 disposed so that the third input shafts 16a and 17a are both rotatably supported by the rotary 3, and a developing device attached to the rotating shaft of the developing device drive motor 11 so as to be integrally rotatable. A motor drive gear 19, a drive gear 20 fixed to the first input shaft 15a so as to be integrally rotatable, and developing rollers attached to the respective rotation shafts of the developing rollers 4a, 5a, 6a and 7a so as to be integrally rotatable. A driving gear 21 (developing roller driving gears of the developing rollers 5a, 6a, and 7a are not shown) and first developing device driving intermediate gears 22 (which are always meshed with the developing roller driving gears 21). The first developing device driving intermediate gears meshed with the developing roller driving gears of the image rollers 5a, 6a, and 7a can be integrally rotated with the rotation shafts of the supply rollers 4b, 5b, 6b, and 7b, respectively. The supply roller drive gears 23 (the supply roller drive gears of the supply rollers 5b, 6b, and 7b are not shown) that are attached to the first developing device and always mesh with the first developing device drive intermediate gears 22, and the supply rollers Second developer drive intermediate gears 24 that are always meshed with the drive gear 23 (the second developer drive intermediate gears meshed with the supply roller drive gears of the supply rollers 5b, 6b, and 7b are not shown), and these The third developing device driving intermediate gears 25 that are concentrically and integrally rotatable with the second developing device driving intermediate gears 24 (the second developing devices on the supplying roller driving gears of the supplying rollers 5b, 6b, and 7b). vessel The third developing device driving intermediate gears that are gear-coupled via the driving intermediate gears are not shown), and the fourth developing device driving intermediate gears 26 that are always meshed with the third developing device driving intermediate gears 25, respectively. (The fourth developer drive intermediate gears connected to the supply roller drive gears of the supply rollers 5b, 6b, and 7b via the second and third developer drive intermediate gears are not shown), and Third to sixth outputs of the fifth developer driving intermediate gears 27 provided concentrically with the fourth developing device driving intermediate gears 26 so as to be integrally rotatable, and the second and third differential gears 16 and 17. Sixth developer drive intermediate gears 28 that are always meshed with one of the gears 16b, 16c, 17b, 17c and always meshed with the fifth developer drive intermediate gear 27 are provided.
[0036]
Among the sixth developing device driving intermediate gears 28, the sixth developing device driving intermediate gear 28 corresponding to the yellow developing device 4 is a plane of the third output gear 16b of the second differential gear 16 as shown in FIG. Gear 16b ₁ The sixth developing device driving intermediate gear 28 corresponding to the magenta developing device 5 is not shown, but the spur gear 16c of the fourth output gear 16c of the second differential gear 16 is not shown. ₁ Further, the sixth developing device driving intermediate gear 28 corresponding to the cyan developing device 6 is also not shown in the figure, but the spur gear 17b of the fifth output gear 17b of the third differential gear 17 is not shown. ₁ The sixth developing device driving intermediate gear 28 corresponding to the black developing device 7 is also not shown in the figure, but the spur gear 17c of the sixth output gear 17c of the third differential gear 17 is also shown. ₁ Always meshed. In FIGS. 1 and 2, the first to fourth locks 16f, 16g, 17f, and 17g of the differential gear mechanism 14 are not shown.
[0037]
Next, rotation control of the developing rollers 4a, 5a, 6a, 7a and the supply rollers 4b, 5b, 6b, 7b by the driving force of the developing device driving motor 11 by the differential gear mechanism 14 will be described. In this description, for the sake of convenience, it is assumed that the developing roller that is to contact the OPC 8 this time is the developing roller 4 a of the yellow developing device 4. In the state shown in FIG. 1, the yellow developing roller 4a is already in contact with the OPC 8 and is in the developing position, that is, the rotational position C of the rotary 3 (hereinafter simply referred to as the position C, and the other rotational positions are the same). The description of the control by the differential gear mechanism 14 starts from a state in which the developing roller 7a of the black developing device 7 is in a position C where the developing roller 7a contacts the OPC 8, and the yellow developing roller 4a is not in this position C. When the developing roller 7a of the black developing device 7 is in the position C, the developing roller 4a of the yellow developing device 4 is in the position A where it does not contact the OPC 8. Further, only the fourth lock 17g is not operated, and only the developing roller 7a is rotated by the driving force of the developing device driving motor 11.
[0038]
In this state, the rotary 3 rotates in the clockwise direction indicated by the arrow, the developing roller 7a of the black developing device 7 that has been in contact with the OPC 8 so far is separated from the OPC 8, and the developing roller 4a rotates and moves toward the position C. To do. As will be described in detail later, the developing device drive motor 11 is stopped thereafter, and the rotation of the developing roller 7a is stopped.
[0039]
When the developing roller 4a is rotationally moved to the position B where it does not come into contact with the OPC 8, the CPU drives the developing device motor 11 and operates the second to fourth locks 16g, 17f, and 17g to cause the fourth to sixth output gears 16c. , 17b, 17c are locked. Then, the driving force of the developing device drive motor 11 is input to the first input shaft 15a of the first differential gear 15, but only the third output gear 16b is not locked, so only the third output gear 16b rotates. To do. The rotation of the third output gear 16b is transmitted to the yellow developing roller 4a and the supply roller 4b via the yellow developing device driving force transmitting means 12Y, and both rollers 4a and 4b start to rotate.
[0040]
When the rotary 3 further rotates in the same direction and the developing roller 4a rotates and moves to the developing position of the position C where it abuts on the OPC 8, the CPU stops the stepping motor 9 for driving the rotary, and the rotation of the rotary 3 stops. At this time, the developing roller 4a continues to rotate at a rotational speed equal to or higher than a predetermined rotational speed.
As described above, the developing roller 4a starts rotating before the OPC 8 comes into contact, and is brought into contact with the OPC 8 while being rotated at a predetermined rotational speed or more to be set at the developing position.
[0041]
Next, when the yellow development is completed, the stepping motor 9 is driven again to rotate the rotary 3 in the same direction again, and the developing roller 4a is separated from the OPC 8 while rotating at a rotational speed equal to or higher than a predetermined rotational speed. When the developing roller 4a rotates and moves to the position D, the CPU stops driving the developing device drive motor 1, and the second to fourth locks 16g, 17f, 17g are deactivated, and the fourth to sixth output gears 16c, 17b and 17c are free to rotate again.
The rotation control of the developing rollers 5a, 6a, 7a and the supply rollers 5b, 6b, 7b by the driving force of the developing device driving motor 11 in the magenta developing device 5, the cyan developing device 6 and the black developing device 7 is also performed. The first to fourth locks 16f, 16g, 17f, and 17g are appropriately selected and operated by the CPU in this order, and the operation is performed in the same manner as in the case of the yellow developing device 4.
[0042]
Next, the operation at the time of image formation of the image forming apparatus 1 of this example configured as described above will be described.
In FIG. 1, the developing roller 4a of the yellow developing device 4 is shown in contact with the OPC 8, but the developing rollers 4a, 5a, 6a, and 7a of the developing devices 4, 5, 6, and 7 are not in contact with each other. During development, both are held at positions separated from the OPC 8. That is, when the image forming apparatus 1 is not in operation, the rotary 3 is stopped and held while the yellow developing device 4a is located between the position A and the position B, and the first to fourth locks 16f, 16g, 17f, and 17g are all inactive.
[0043]
When the operation of the image forming apparatus 1 is started for image formation, the CPU of the image forming apparatus 1 drives the stepping motor 9 to rotate the rotary 3 clockwise, and the yellow developing roller 4a is at the position B. Move to rotate. When the developing roller 4a reaches the position B, the developing device drive motor 11 is driven as described above, and the second to fourth locks 16g, 17f, and 17g are operated, and the fourth to sixth output gears 16c, Both 17b and 17c are locked, and only the third output gear 16b rotates. As a result, both the developing roller 4a and the supply roller 4b of the yellow developing device 4 rotate.
[0044]
When the rotary roller 3 further rotates in the same direction and the developing roller 4a reaches a position C where the developing roller 4a contacts the OPC 8 which is the developing position after a predetermined time has elapsed, the rotation of the rotary roller 3 stops. Since a predetermined time elapses from when the developing roller 4a starts to rotate to the developing position and there is a margin for the rotation rise time of the developing roller 4a, when the developing roller 4a reaches the developing position, the developing roller 4a is predetermined. Rotating above the number of rotations. Therefore, the toner is uniformly dispersed on the developing roller 4a, and a toner layer having a predetermined thickness is securely formed on the surface of the developing roller 4a. When the developing roller 4a contacts the OPC 8, damage to the OPC 8 is prevented. Is done. As a result, the developing roller 4a conveys a predetermined amount of toner toward the OPC 8, and the latent image on the OPC 8 is developed in yellow. The developed yellow image on the OPC 8 is intermediately transferred to the intermediate transfer medium 29.
When the yellow developing roller 4a is at position C, the developing roller 4a of the next magenta developing device 5 is at position A as shown in FIG.
[0045]
When the yellow development is completed, the rotary 3 rotates again in the same direction, and the developing roller 4a moves away from the OPC 8 while rotating at a predetermined rotational speed or more. When the developing roller 4a reaches the position D, the driving of the developing device drive motor 11 stops, the rotation of the developing roller 4a and the supply roller 4b stops, and the second to fourth locks 16c, 17f, 17g are all. The fourth to sixth output gears 16c, 17b, and 17c are free to rotate.
[0046]
When the developing roller 5a of the magenta developing device 5 reaches the position B by the further rotation of the rotary 3, the developing device drive motor 11 is driven in the same manner as in the case of the yellow developing device 4, and the first, The third and fourth locks 16f, 17f and 17g are actuated, and the third, fifth and sixth output gears 16b, 17b and 17c are all locked. As a result, the developing roller 5a rotates. Thereafter, the developing operation by the magenta developing device 5 is performed in the same manner as the developing operation by the yellow developing device 4, whereby the magenta development is performed on the latent image on the OPC, and the development on the OPC is performed. The magenta image thus obtained is intermediately transferred to the intermediate transfer medium 29.
[0047]
Subsequently, in the same manner as yellow development by the yellow developing device 4, cyan development by the cyan developing device 6 and black development by the black developing device 7 are sequentially performed by not operating the corresponding locks. Each developed image is intermediately transferred to the intermediate transfer medium 29. The four-color images intermediately transferred to the intermediate transfer medium 29 are color-matched, transferred to transfer paper by a transfer device (not shown), and fixed by a fixing device, thereby forming a full-color image.
[0048]
Incidentally, it is necessary to initialize the image forming apparatus 1 before the user uses the image forming apparatus 1 shipped from the factory. When the image forming apparatus 1 is initialized, a predetermined amount of toner must be supplied to the developing roller to form a toner layer on the surface of the developing roller in order to prevent OPC damage due to contact with the developing roller. Don't be. Accordingly, the image forming apparatus 1 of this example further includes the developing rollers 4a, 5a, 4a, 4a, 5a, 6a, 7a in a state where the rotary 3 is stopped at a position where none of the four developing rollers 4a, 5a, 6a, 7a contacts the OPC 8. A predetermined amount of toner is supplied to each developing roller 4a, 5a, 6a, 7a by rotating both 6a, 7a.
That is, as shown in FIG. 1, each of the four developing rollers 4a, 5a, 6a, and 7a is in an arbitrary position where the OPC 8 does not come into contact with the initialization position E. _Y , E _M , E _C , E _K Is set.
[0049]
In initializing the image forming apparatus 1 shipped from the factory, first, the stepping motor 9 is driven to rotate the rotary 3, and the developing rollers 4a, 5a, 6a, and 7a are respectively initialized to the initialization position E. _Y , E _M , E _C , E _K At this time, the driving of the stepping motor 9 is stopped by the CPU, and the rotation of the rotary 3 is stopped. Next, when the developing device drive motor 11 is driven by the CPU and the first input shaft 15a of the first differential gear 15 is rotated, the first to fourth locks 16f, 16g, 17f, 17g are inoperative and the third Since the sixth output gears 16b, 16c, 17b, and 17c are freely rotatable, the developing rollers 4a, 5a, 6a, and 7a and the supply rollers 4b, 5b, 6b, and 7b are rotated together, and the developing rollers are rotated. The toner is supplied to 4a, 5a, 6a, and 7a, and a toner layer having a predetermined thickness is formed on the surfaces thereof. Thereby, the image forming apparatus 1 is initialized in a short time without damaging the OPC 8.
[0050]
As described above, according to the image forming apparatus 1 of this example, when the developing rollers 4a, 5a, 6a, and 7a are brought into contact with the OPC 8, respectively, the developing rollers 4a, 5a, 6a, and 7a are always rotated. In this case, the developing rollers 4a, 5a, 6a, and 7a can always be brought into contact with the OPC 8 while being rotated at a predetermined rotational speed or more. Further, when the developing rollers 4a, 5a, 6a, and 7a are separated from the OPC 8, respectively, the developing rollers 4a, 5a, 6a, and 7a can be separated from the OPC 8 in a state in which they are always rotated. In this case, the developing rollers 4a, 5a, 6a, 7a can be separated from the OPC 8 while being rotated at a predetermined rotational speed or more. As a result, the developing rollers 4a, 5a, 6a, 7a and the supply rollers 4c, 5c, 6c, 7c are rotated when the developing rollers 4a, 5a, 6a, 7a are brought into contact with and separated from the OPC 8, so that the developing rollers 4a, 5a , 6a, 7a can form a toner layer having a predetermined thickness. Accordingly, the developing rollers 4a, 5a, 6a, and 7a can be brought into contact with and separated from the OPC 8 through the toner layer, and the toner functions as a lubricant, so that damage to the OPC 8 can be effectively prevented.
[0051]
Further, the developing rollers 4a, 5a, 6a, and 7a and the supply rollers 4c, 5c, 6c, and 7c are rotationally driven only in a predetermined area including the developing position, and the rotation is stopped in other areas. Toner scattering can be suppressed.
Furthermore, according to the image forming apparatus 1 of this example, in the initialization after shipment from the factory, the four developing rollers 4a are located at positions where none of the developing rollers 4a, 5a, 6a, 7a is in contact with the OPC 8. , 5a, 6a, 7a can be driven to reliably form a toner layer on the surface of each developing roller 4a, 5a, 6a, 7a, so that the OPC 8 can be initialized in a short time without damaging it. It can be performed. This eliminates the need to apply dummy toner to the surfaces of the developing rollers 4a, 5a, 6a, and 7a, which has been conventionally performed at the time of factory shipment. Will be easier.
Furthermore, since no dummy toner is required, the cost can be reduced and only the toner for image formation is used, so that the toner can be recycled.
[0052]
In the above-described example, three differential gears α are used to obtain four outputs with respect to the driving force of one developing device driving motor 11, and these four outputs are respectively provided to four developing devices. Although transmitted to the four developing rollers 4a, 5a, 6a, and 7a of 4, 5, 6, and 7, the present invention is not limited to this.
That is, for example, as in the case of the differential gear α shown in FIG. 5, two outputs are obtained with respect to the driving force of one developing device driving motor 11 by one differential gear α. Each output can be transmitted to two developing rollers of two developing units.
[0053]
For example, in the differential gear mechanism 14 shown in FIG. 6, the third differential gear 17 is omitted, and a lock for stopping the rotation of the second output gear 15 c is provided, so that the second output gear of the first differential gear 15 is provided. It is also possible to take out the output directly from 15c. In this case, three outputs are obtained with respect to the driving force of one developing device driving motor 11 by two differential gears α, and these three outputs are respectively supplied to three developing devices. To the developing roller.
[0054]
Further, in the differential gear mechanism 14 shown in FIG. 6, another differential gear α is used, and the third to sixth output gears 16b, 16c, 17b, 17c of the second and third differential gears 17 are used. The input shaft of the other differential gear α can be connected to one of them via an intermediate power transmission gear similar to the first and second intermediate power transmission gears 16h, 17h. In this case, five outputs are obtained with respect to the driving force of one developing device driving motor 11 by four differential gears α, and these five outputs are respectively supplied to five developing devices. To the developing roller. At this time, it goes without saying that the lock of the output gear meshed with the newly added intermediate power transmission gear among the third to sixth output gears 16b, 16c, 17b, 17c is omitted. Similarly, another one of the differential gears α is used, and another one of the third to sixth output gears 16b, 16c, 17b, 17c of the second and third differential gears 17 is used. Similarly, the input shaft of this further differential gear α can be connected via an intermediate power transmission gear. In this case, six outputs are obtained with respect to the driving force of one developing device driving motor 11 by five differential gears α, and these six outputs are respectively supplied to six developing devices. To the developing roller.
[0055]
As described above, in the present invention, n differential gears α are used for n developing rollers of n developing devices, and n developing rollers are driven by one developing device driving motor 11. The n outputs can be transmitted to the n developing rollers.
[0056]
Furthermore, in the above-described example, the present invention is described by applying to a full-color image forming apparatus having an intermediate transfer medium. However, the present invention is not limited to two or more single-color image forming apparatuses or the like. The image forming apparatus can be applied to any image forming apparatus in which n developing devices are mounted on the rotating body and the developing roller is in contact with the photosensitive member.
[0057]
【The invention's effect】
As is apparent from the above description, according to the image forming apparatus of the present invention, the output of the differential gear mechanism is selected before the developing roller that is in contact with the photosensitive member reaches the developing position in contact with the photosensitive member. The developer driving motor driving force is reliably transmitted via a differential gear mechanism to a developing roller that is about to come into contact with the photosensitive member before the developing position is brought into contact with the photosensitive member. Since the developing roller is always in contact with and separated from the photoconductor while reliably rotating, a toner layer can be formed on the surface of the developing roller when the developing roller is in contact with and separated from the photoconductor. As a result, the developing roller can be brought into contact with and separated from the photoreceptor via the toner layer, and the toner functions effectively as a lubricant, thereby effectively preventing damage to the photoreceptor. Therefore, a high quality image can be formed and the life of the image forming apparatus can be improved.
[0058]
In particular, according to the third aspect of the present invention, since the developing roller is always in contact with the photosensitive member in a state of being rotated at a predetermined rotational speed or more, toner can be supplied to the developing roller more reliably, It is possible to more reliably prevent the photoreceptor from being damaged when the roller contacts.
According to the fourth aspect of the present invention, since the developing roller is always reliably rotated at a predetermined rotation speed or more and is brought into contact with the photosensitive member after a predetermined time has elapsed, the toner is uniformly applied to the developing roller. While being able to disperse | distribute, the rotation fluctuation | variation of a developing roller can be suppressed. As a result, the toner layer can be uniformly formed on the developing roller, and the rotational fluctuation of the developing roller can be reduced, so that the photoreceptor can be more reliably prevented from being damaged. Therefore, it is possible to form a higher quality image and to further extend the life of the image forming apparatus.
[0059]
Further, according to the invention of claim 5, since the developing roller is always separated from the photosensitive member in a state of rotating at a predetermined rotation speed or more, the developing roller is operated in a state in which the toner is more reliably supplied to the developing roller. The photosensitive member can be separated from the photosensitive member, and damage to the photosensitive member can be more reliably prevented when the developing roller is separated.
[0060]
Furthermore, according to the invention of claim 6, since two or more developing rollers can be rotated in a state in which none of the developing rollers is in contact with the photoconductor, image formation is performed after shipment from the factory without damaging the photoconductor. The device can be easily initialized in a short time. This also eliminates the need to apply dummy toner to the surface of each developing roller, which has been conventionally performed at the time of factory shipment, eliminating the need for dummy toner application at the time of factory shipment and simplifying the operation at the time of shipment. be able to.
Furthermore, since no dummy toner is required, the cost can be reduced and only the toner for image formation is used, so that the toner can be recycled.
[Brief description of the drawings]
FIG. 1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus of the present invention.
FIG. 2 shows a differential gear mechanism and a power transmission mechanism of a rotary portion along the line II-II in FIG. 1, and shows a portion of the power transmission mechanism other than the developing roller, the supply roller, and the differential gear mechanism. 1 is a diagram showing the state as viewed from the left side in FIG.
FIG. 3 is a partial cross-sectional view corresponding to a part of FIG. 2, showing an example of a method of connecting a rotary shaft and a rotary gear to a rotary shaft.
4 is a partial cross-sectional view showing a part taken along the line IV-IV shown in FIG. 3;
5 explains the operation of a differential gear, which is the basic configuration of the differential gear mechanism used in the image forming apparatus of the example shown in FIG. 1, and (a) outputs both from two output gears. FIG. 4B is a diagram illustrating output from one of the two output gears, and FIG. 5C is output from the other output gear of the two output gears. FIG.
6 is a diagram for explaining the operation of the differential gear mechanism of the image forming apparatus of the example shown in FIG. 1 configured using three differential gears shown in FIG. 5;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Developing device, 3 ... Rotary, 4 ... Yellow developing device, 5 ... Magenta developing device, 6 ... Cyan developing device, 7 ... Black developing device, 4a, 5a, 6a, 7a ... Developing roller, 4b, 5b, 6b, 7b... Feed roller, 8. ... Developer driving force transmission means, 13 ... Frame, 14 ... Intermediate transfer medium, 15 ... First differential gear, 15a ... First input shaft, 15b ... First output gear, 15b ₁ ... First spur gear, 15b ₂ ... 1st bevel gear, 15c ... 2nd output gear, 15c ₁ ... Second spur gear, 15c ₂ ... second bevel gear, 15d ... first power transmission shaft, 15e ... first intermediate bevel gear, 16 ... second differential gear, 16a ... second input shaft, 16b ... third output gear, 16b ₁ ... Third spur gear, 16b ₂ ... 3rd bevel gear, 16c ... 4th output gear, 16c ₁ ... 4th spur gear, 16c ₂ ... 4th bevel gear, 16d ... 2nd power transmission shaft, 16e ... 2nd intermediate bevel gear, 16f ... 1st lock, 16g ... 2nd lock, 16h ... 1st intermediate power transmission gear, 17 ... 3rd differential gear , 17a ... third input shaft, 17b ... fifth output gear, 17b ₁ ... Fifth spur gear, 17b ₂ ... Fifth bevel gear, 17c ... Sixth output gear, 17c ₁ ... Sixth spur gear, 17c ₂ ... 5th bevel gear, 17d ... 3rd power transmission shaft, 17e ... 3rd intermediate bevel gear, 17f ... 3rd lock, 17g ... 4th lock, 17h ... 2nd intermediate power transmission gear, C ... To OPC of developing roller Contact position

Claims (6)

N developing devices each having a developing roller mounted on a rotating body and capable of contacting and separating from the photosensitive member, the developing roller being separated from the photosensitive member during non-development, and driving of a developing device drive motor during development Force is transmitted in sequence to the developing roller via a developing device driving force transmission means provided for each developing device, and the rotating roller moves the developing roller to a developing position in contact with the photoconductor in order. In the image forming apparatus for performing multi-color development by setting the developing position at the rotation stop of the rotating body,
The developing device driving force transmission means includes a differential gear mechanism composed of n-1 differential gears, and the differential gear is at least rotated relative to the input shaft and is rotated relative to the input shaft. Two output gears each provided with a bevel gear , and capable of revolving around the input shaft by rotation of the input shaft and capable of rotating about an axis orthogonal to the input shaft, The bevel gears that are always meshed with any of the bevel gears of the two output gears and that are other than the bevel gears of the two output gears ,
The differential gear mechanism transmits the driving force of the developing device drive motor to the input shaft of one of the n-1 differential gears , and the first differential gear. the are two output gear one of the output of the first and second output gears, among the (n-1) of the differential gear, it is transmitted to the input shaft of the other one of the second differential gear in with that, one of the output one of the other output of the respective output and first and second output gears of the third and fourth output gear is the two output gears in the second differential gear the one of the n-1 of the differential gear, is connected further so as to be transmitted to the input shaft of the other one of the third differential gear, the n-1 of the differential gear, respectively, the n -Of each output gear of one differential gear, the other differential gear The output is output from an output gear whose output is not transmitted to the force shaft, and n outputs are obtained by the n-1 differential gears with respect to the driving force of the developing device drive motor. Are transmitted to each of the n developing rollers,
N is n ≧ 3;
Furthermore, a control means for controlling the differential gear mechanism so as to selectively extract an arbitrary number of outputs among the n outputs is provided, and the control means is applied to the photosensitive member by the rotation of the rotating body. The differential gear mechanism is controlled so that the output is taken out before the developing roller to be contacted reaches the developing position where the developing roller comes into contact with the photosensitive member, and the developing roller moves from the developing position and moves to the photosensitive position. An image forming apparatus, wherein the differential gear mechanism is controlled to stop taking out the output after being separated from the body. Two developing devices each having a developing roller mounted on a rotating member and capable of contacting and separating from the photosensitive member are provided, the developing roller is separated from the photosensitive member during non-development, and the developing device drive motor is driven during development. Force is transmitted in sequence to the developing roller via a developing device driving force transmission means provided for each developing device, and the rotating roller moves the developing roller to a developing position in contact with the photoconductor in order. In the image forming apparatus for performing multi-color development by setting the developing position at the rotation stop of the rotating body,
The developing device driving force transmission means includes a differential gear mechanism composed of one differential gear, and the differential gear can at least rotate relative to the input shaft and can only rotate relative to the input shaft. Two output gears each having a bevel gear, revolving around the input shaft by rotation of the input shaft, and capable of rotating about an axis orthogonal to the input shaft. Each of the bevel gears of each of the two output gears is always meshed with each other, and the bevel gears other than the respective bevel gears of the two output gears,
The differential gear mechanism is configured to transmit the driving force of the developing device drive motor to an input shaft of the differential gear, and to take out outputs from the two output gears in the differential gear, With respect to the driving force of the developing device driving motor, two outputs are obtained by the one differential gear, and these two outputs are transmitted to the two developing rollers, respectively. And
Further, a control means for controlling the differential gear mechanism so as to selectively extract at least one of the two outputs is provided, and the control means is applied to the photoconductor by the rotation of the rotating body. The differential gear mechanism is controlled so that the output is taken out before the developing roller to be brought into contact with the photosensitive member reaches the developing position, and the developing roller moves from the developing position to move the photosensitive member. An image forming apparatus, wherein the differential gear mechanism is controlled so as to stop taking out the output after being separated from the image forming apparatus. The rotating body sets the developing roller at the developing position when the developing roller rotated by the output of the differential gear mechanism selectively taken out by the control means reaches a predetermined number of rotations or more. the image forming apparatus according to claim 1 or 2, wherein the is brought into contact with the photoreceptor Te. The rotating body rotates the developing roller rotated by the output of the differential gear mechanism selectively picked up by the control means after the predetermined number of rotations has elapsed and a predetermined time has elapsed. claim 1 or 2 image forming apparatus wherein it is brought into contact with the photosensitive member is set to the position. The rotating body moves the developing roller from the developing position when the developing roller rotated by the output of the differential gear mechanism selectively taken out by the control means is at a predetermined rotational speed or more. the image forming apparatus according to claim 1 or 2, wherein the to separate from the photoreceptor. Each developing roller is rotated by the output of the differential gear mechanism selectively taken out by the control means in a state where the rotating body is set to a position where none of the developing rollers contacts the photoconductor. the image forming apparatus as claimed in any one of claims 1 and performs initialization 5 by.

Images